Hyaluronate and its derivatives for customized biomedical applications.

Since hyaluronate (HA) was firstly isolated from the vitreous of bovine eyes in 1934, HA has been widely investigated for various biomedical applications. As a naturally-occurring polysaccharide, HA has been used for joint lubrication and ocular treatment in its intact form due to the excellent biocompatibility, viscoelasticity, biodegradability, and hygroscopic properties. HA can be easily functionalized via the chemical modification of its carboxyl and hydroxyl groups. Recently, a variety of biological functions of HA have been explored and a number of customized applications have been investigated taking advantages of the interaction between HA and biological tissues. HA has been used for drug delivery to enhance the blood circulation time of drugs with target-specificity to HA receptors in the body. HA has been also used to prepare tissue engineering hydrogel scaffolds for the spatiotemporal control of encapsulated cells. In this review, we describe the key biological functions of HA in the body in terms of its structure, physical properties, biodistribution and interaction with HA receptors. After that, we describe unique advantages that allow HA to be applied in various biomedical fields. Finally, we report the conventional and newly emerging applications of HA and its derivatives under commercial development stages.

Hyaluronate-Epidermal Growth Factor Conjugate for Skin Wound Healing and Regeneration.

Epidermal growth factor (EGF) has been recognized as an excellent wound healing agent due to its therapeutic function stimulating skin cell growth, proliferation and differentiation. However, the transdermal delivery of EGF poses a significant challenge due to its short half-life and lack of efficient formulation. Here, to improve the transdermal delivery efficiency, EGF was conjugated to hyaluronate (HA), which was formulated into a patch-type film for skin wound healing. HA-EGF conjugate was synthesized by coupling reaction between aldehyde-modified HA and N-terminal amine group of EGF to minimize the loss of biological activities. The HA-EGF conjugates exhibited similar biological activities with native EGF as confirmed by ELISA and proliferation tests using murine and human fibroblasts. For the efficient topical delivery, HA-EGF conjugates were incorporated into a matrix film of high molecular weight HA. Two-photon microscopy clearly visualized more efficient transdermal delivery of HA-EGF conjugates to both normal skin and peripheral tissues around the wound area rather than that of EGF. Optical imaging and ELISA after in vivo transdermal delivery showed that the conjugation of EGF to HA retarded its degradation and extended its residence time in the wound area. Furthermore, in vivo transdermal delivery of HA-EGF conjugate in the patch-type HA film resulted in significantly improved regeneration of skin tissues even into hypodermis.

Genetically engineered mesenchymal stem cell therapy using self-assembling supramolecular hydrogels.

Stem cell therapy has attracted a great deal of attention for treating intractable diseases such as cancer, stroke, liver cirrhosis, and ischemia. Especially, mesenchymal stem cells (MSCs) have been widely investigated for therapeutic applications due to the advantageous characteristics of long life-span, facile isolation, rapid proliferation, prolonged transgene expression, hypo-immunogenicity, and tumor tropism. MSCs can exert their therapeutic effects by releasing stress-induced therapeutic molecules after their rapid migration to damaged tissues. Recently, to improve the therapeutic efficacy, genetically engineered MSCs have been developed for therapeutic transgene expression by viral gene transduction and non-viral gene transfection. In general, the number of therapeutic cells for injection should be more than several millions for effective cell therapy. Adequate carriers for the controlled delivery of MSCs can reduce the required cell numbers and extend the duration of therapeutic effect, which provide great benefits for chronic disease patients. In this review, we describe genetic engineering of MSCs, recent progress of self-assembling supramolecular hydrogels, and their applications to cell therapy for intractable diseases and tissue regeneration.